title: Arabidopsis J-protein J20 delivers the first enzyme of the plastidial isoprenoid pathway to protein quality control.
abstract: Plastids provide plants with metabolic pathways that are unique among eukaryotes, including the methylerythritol 4-phosphate pathway for the production of isoprenoids essential for photosynthesis and plant growth. Here, we show that the first enzyme of the pathway, deoxyxylulose 5-phosphate synthase (DXS), interacts with the J-protein J20 in Arabidopsis thaliana. J-proteins typically act as adaptors that provide substrate specificity to heat shock protein 70 (Hsp70), a molecular chaperone. Immunoprecipitation experiments showed that J20 and DXS are found together in vivo and confirmed the presence of Hsp70 chaperones in DXS complexes. Mutants defective in J20 activity accumulated significantly increased levels of DXS protein (but no transcripts) and displayed reduced levels of DXS enzyme activity, indicating that loss of J20 function causes posttranscriptional accumulation of DXS in an inactive form. Furthermore, J20 promotes degradation of DXS following a heat shock. Together, our data indicate that J20 might identify unfolded or misfolded (damaged) forms of DXS and target them to the Hsp70 system for proper folding under normal conditions or degradation upon stress.
authors.affiliation: Centre for Research in Agricultural Genomics, CSIC-IRTA-UAB-UB, 08193 Barcelona, Spain.
authors.forename: Pablo
authors.initials: P
authors.lastname: Pulido
authors.forename: Gabriela
authors.initials: G
authors.lastname: Toledo-Ortiz
authors.forename: Michael A
authors.initials: MA
authors.lastname: Phillips
authors.forename: Louwrance P
authors.initials: LP
authors.lastname: Wright
authors.forename: Manuel
authors.initials: M
authors.lastname: Rodríguez-Concepción
mesh_terms: D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D002736:Chloroplasts / Q000201:enzymology*; D018506:Gene Expression Regulation, Plant; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism; D053858:Metabolic Networks and Pathways; D030821:Plants, Genetically Modified / Q000201:enzymology / Q000235:genetics; D025941:Protein Interaction Mapping; D013729:Terpenes / Q000378:metabolism*; D014166:Transferases / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D018840:HSP70 Heat-Shock Proteins; D013729:Terpenes; D014166:Transferases; C109461:deoxyxylulose-5-phosphate synthase